Cossack is located on Butcher Inlet at the mouth of the Harding River. It is reached by a single, sealed road that follows the original causeway across a series of tidal salt flats. The overall landform of the region around Cossack is a low, flat plain with occasional rocky hills and ranges. The vegetation is mainly grass, spinifex and low shrub, with occasional trees along watercourses and in gullies. The scrub becomes quite dense along the shoreline and at the mouth of the inlet.
The main road from Roebourne to Cossack continues past the town of Wickham and the Cape Lambert iron ore loading facility (operated by Pilbara Iron), and terminates at the fishing town of Point Samson. The townsite is not visible from the main road, and only becomes apparent as the road rounds Nanny Goat Hill.
The site of the former town is defined by Nanny Goat Hill, Tien Tsin Lookout, the hilly ground to the north-east and north-west, and Butchers Inlet to the west and south-west. Past the townsite, the road winds up to Tien Tsin Lookout, from which sweeping views of the surrounding coastline can be seen. Many of the buildings are listed by the National Trust.
In May 1863, Walter Padbury landed his stock at the mouth of the Harding River near the present site of Cossack. Cossack was first known as Tien Tsin, or Port Tientsin, after the barque that carried Padbury and his party. The ship that brought the state's Governor, Frederick Weld, in December 1871 was named Cossack and the town adopted this name in 1872. Cossack was the first port in the North West, and was critical to the development of the pastoral industry in the region.
In 1881 a cyclone damaged the town, and every pearling vessel then operating either foundered or was beached. In 1885, 44 vessels were operating out of Cossack, however in that year a Select Committee recommended the closure of several pearling banks in the area due to depletion. In 1886 the main pearling industry moved to Broome.
During the 1870s a causeway was built across the tidal salt flats that separate Cossack from the main road. The causeway still forms the only access to the town from land. A horse-drawn tramway between Roebourne and Cossack was completed in 1887, the same year that the municipality of Cossack was declared, and the North West gold rush commenced.
The main stone buildings were constructed in the 1880s. Administrative and other public buildings built there in the 1890s continued a style adopted by the emerging state; these have been surveyed by state heritage groups and they found them to be architecturally and historically significant.
Following the move of the pearling industry to Broome and the decline of the gold rush, the population of Cossack dwindled. The harbour proved unsuitable for the larger ships of the early 20th century. Between 1902 and 1904 a jetty was constructed at the nearby town of Point Samson. In 1910 the port moved there and the municipality of Cossack was dissolved. In 1913 a leprosarium was established on the other side of the river, moving to Darwin in 1930. The town became derelict and was abandoned in the 1950s.
The region is subject to violent storms and cyclones and was severely damaged at different times in its history. Its use as a port for the profitable pearling industry and other economic booms saw investment and backing from Perth and it remained an important northern port. The town was abandoned after the 1940s, leaving the sometimes substantial stone buildings in a state of disrepair. The state government established a survey, in 2007, into the potential for restoration or revitalisation of this remote town.
Cossack contains a small cemetery in two parts - one European and one Japanese. The pearling industry of the 19th century was notably dangerous, with many pearlers losing their lives. Those buried in the Japanese cemetery were mainly divers and others involved with the pearling industry; others, including many Aboriginals, were lost at sea. The first interment in the cemetery is believed to have taken place in 1869, when a man died while walking to Port Walcott in January and was buried there.
At least 41 Europeans and 7 Japanese were buried there, with the last recorded interment occurring in 1915. Those buried there include William Shakespeare Hall.